Bioenergetics — In which eukaryotic organelle do most reactions occur that extract energy from sugar breakdown to synthesize large amounts of ATP?

Introduction / Context:
ATP production is central to cell viability. After glycolysis, most ATP in aerobic eukaryotic cells is produced by oxidative phosphorylation, which is localized to a specific organelle.

Given Data / Assumptions:

• Sugars are catabolized to pyruvate by glycolysis in the cytosol.
• Further oxidation and ATP synthesis require electron transport and chemiosmosis.
• Organelles compartmentalize these processes in eukaryotes.

Concept / Approach:
Mitochondria host the citric acid cycle, electron transport chain on the inner membrane, and ATP synthase that uses the proton gradient to generate ATP. While minor ATP arises elsewhere, mitochondria are the powerhouse for bulk ATP under aerobic conditions.

Step-by-Step Solution:

Verification / Alternative check:
Oxygen consumption and ATP production assays localize to mitochondria; removal or dysfunction of mitochondria diminishes ATP output.

Why Other Options Are Wrong:

• Lysosomes digest macromolecules; they do not synthesize ATP.
• Vesicles are transport compartments, not ATP factories.
• Plasma membrane participates in prokaryotic respiration, but in eukaryotes oxidative phosphorylation is mitochondrial.
• Peroxisomes carry out oxidation reactions and detoxification, not bulk ATP generation.

Common Pitfalls:
Assuming glycolytic ATP equals total ATP; oxidative phosphorylation typically dominates energy yield.

Final Answer:
Mitochondria